In some voice-over-Internet-Protocol (VoIP) networks, it may be desirable to provide voicemail services that customers may access using a single access number (e.g., a toll-free number). Customers may dial the single access number whether on-net (e.g., calling from a recognized device associated with an account in the VoIP network) or off-net to access their voice mailboxes. In some networks, customer accounts may be distributed among multiple voicemail systems. On-net VoIP calls to the single access number are typically routed to a single application server, from which a customer's call may be routed to the appropriate voicemail system. Using a single application server to manage all calls for multiple voicemail systems may eventually overload the application server.